gui: single-line session rows — drop the persona/workspace subtitle

Personas are disabled for the first release, so the subtitle repeated the same
label on every row. When personas return they surface on hover, not as a second
line. UX-DECISIONS §7 updated; e2e spec added.

surfaces/gui/e2e/sidebar-rows.spec.ts

@@ -0,0 +1,15 @@
+import { test, expect } from "./fixtures";
+
+// Session rows are SINGLE-LINE (UX-DECISIONS §7, 2026-07-21): title only — the
+// persona/workspace subtitle is gone (personas are launch-flagged off; when they return
+// the persona surfaces on hover, not as a second line).
+test("recent session rows render the title only — no persona subtitle", async ({ page }) => {
+  await page.goto("/");
+  const row = page
+    .locator(".sidebar .group")
+    .filter({ hasText: "Draft the launch note" })
+    .first();
+  await expect(row).toBeVisible();
+  const text = (await row.innerText()).trim();
+  expect(text).toBe("Draft the launch note");
+});